Tag: Laser-Induced Graphene

Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability

Post author By Alexander Dallinger
Post date July 11, 2023

“Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability”

Dallinger, Alexander, Felix Steinwender, Matthias Gritzner, and Francesco Greco
Publication Date: July 10, 2023
https://doi.org/10.1021/acsanm.3c02066

Abstract

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of Φ_RO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for “lab-on-chip” applications.

Tags fog basking, Francesco Greco, high contrast, hydrophilic, hydrophobic, Laser-Induced Graphene, millifluidics, patterning, superhydrophobicity, tunable wettability, wettability

News

Paper on sweat analysis featured in a SciLight by AIP

Post author By lampse
Post date October 18, 2022

AIP SciLight

The latest publication on “Sweat analysis with a wearable sensing platform based on laser-induced graphene” was featured in a AIP SciLight. From the AIP: “A Scilight, a science highlight, briefly summarizes newly published research, emphasizing its significance to a particular field. Scilights are written to ‘intrigue’ a broad scientific audience showcasing what is new and important in the latest research.”

Find the article “Don’t sweat it: laser-induced graphene monitors analytes in sweat ” by Ashley Piccone here: https://aip.scitation.org/doi/10.1063/10.0014459

Vivaldi, F., A. Dallinger, N. Poma, A. Bonini, D. Biagini, P. Salvo, F. Borghi, A. Tavanti, F. Greco, and F. Di Francesco
Publication Date: 19 September 2022
https://doi.org/10.1063/5.0093301

Tags biosensor, Francesco Greco, Laser-Induced Graphene, sampler, sweat, wearables

News Publications

Sweat analysis with a wearable sensing platform based on laser-induced graphene

Post author By Alexander Dallinger
Post date October 12, 2022

“Sweat analysis with a wearable sensing platform based on laser-induced graphene”

Vivaldi, F., A. Dallinger, N. Poma, A. Bonini, D. Biagini, P. Salvo, F. Borghi, A. Tavanti, F. Greco, and F. Di Francesco
Publication Date: 19 September 2022
https://doi.org/10.1063/5.0093301

Abstract

The scientific community has shown increasing interest in laser scribing for the direct fabrication of conductive graphene-based tracks on different substrates. This can enable novel routes for the noninvasive analysis of biofluids (such as sweat or other noninvasive matrices), whose results can provide the rapid evaluation of a person’s health status. Here, we present a wearable sensing platform based on laser induced graphene (LIG) porous electrodes scribed on a flexible polyimide sheet, which samples sweat through a paper sampler. The device is fully laser manufactured and features a two layer design with LIG-based vertical interconnect accesses. A detailed characterization of the LIG electrodes including pore size, surface groups, surface area in comparison to electroactive surface area, and the reduction behavior of different LIG types was performed. The bare LIG electrodes can detect the electrochemical oxidation of both uric acid and tyrosine. Further modification of the surface of the LIG working electrode with an indoaniline derivative [4-((4-aminophenyl)imino)-2,6-dimethoxycyclohexa-2,5-dien-1-one] enables the voltammetric measurement of pH with an almost ideal sensitivity and without interference from other analytes. Finally, electrochemical impedance spectroscopy was used to measure the concentrations of ions through the analysis of the sweat impedance. The device was successfully tested in a real case scenario, worn on the skin during a sports session. In vitro tests proved the non-cytotoxic effect of the device on the A549 cell line.

Tags biosensor, Francesco Greco, Laser-Induced Graphene, sampler, sweat, wearables

News Publications

Published chapter in Nanoporous Carbons for Soft and Flexible Energy Devices

Post author By Alexander Dallinger
Post date January 17, 2022

LAMPSe was invited to contribute a chapter to the book “Nanoporous Carbons for Soft and Flexible Energy Devices“.

The chapter with the name “Laser-Induced Graphene and Its Applications in Soft (Bio)Sensors” features an overview from formation of LIG, properties to the application in soft (bio)sensors.

Abstract

In recent years the technological importance of graphene increased significantly also in the field of soft, flexible and wearable electronics. In this chapter a simple one step process to create 3D porous graphene structures into flexible polymer films is highlighted. By laser scribing polymer precursor substrates with commercially available laser scribing setups the polymer is converted into so-called Laser-Induced Graphene (LIG) via a photothermal conversion. The properties of this material and the influence of different processing parameters on its composition and structure are introduced. Different transfer methods for stretchable applications are discussed. Three main application fields of LIG for soft (bio)sensors are identified: piezoresistive, electrophysiological and electrochemical sensors. Each of the application fields is highlighted more in detail and an overview of recent publications is given. Concluding with an outlook on the future of LIG – including improvement of patterning resolution and the use of renewable, bio-derived precursors – this chapter provides a broad overview of LIG for soft and flexible sensor devices.

Tags biosensors, book, Francesco Greco, Laser-Induced Graphene, LIG

News

Third place at TU Graz SciPix audience vote

Post author By lampse
Post date October 1, 2021

LAMPSe is proud to anounce that Francesco Greco and Matthias Gritzner won the third price in the audience vote of the photo competition held at TU Graz called TU Graz SciPix.

The photos show examples of the everyday research at TU Graz.

Francesco Greco was participating with a photo made by Matthias Gritzner during his bachelor thesis and shows UV ink contained in microfluidic channels made from hydrophilic and hydrophobic LIG.

Liquid Yin&Yang on laser induced graphene
A Yin&Yang symbol is formed by self-guidance and mixing of fluorescent dyes in water on top of a pattern of Laser Induced Graphene with tunable wettability (superhydrophilic/superhydrophobic).

Here you can see video of the microfluidics created with LIG. Fluorescent dyes are deposited on the LIG tracks and are guided down to the bottom because of the hydrophilic properties. At the bottom they come in contact with each other and form a Yin&Yang symbol. The liquid is confined by the hydrophobic LIG on the outside.

Tags Francesco Greco, Laser-Induced Graphene, LIG, microfluidics, press, SciPix, superhydrophobic, TU Graz

News Publications

Paper on Printed and Laser-Scribed Stretchable Conductors on Thin Elastomers for Soft and Wearable Electronics

Post author By lampse
Post date August 14, 2021

“Printed and Laser-Scribed Stretchable Conductors on Thin Elastomers for Soft and Wearable Electronics”

Kirill Keller, David Grafinger and Francesco Greco
Publication Date: August 12, 2021
https://doi.org/10.3389/fmats.2021.688133

Abstract

As printed electronics is evolving toward applications in biosensing and wearables, the need for novel routes to fabricate flat, lightweight, stretchable conductors is increasing in importance but still represents a challenge, limiting the actual adoption of ultrathin wearable devices in real scenarios. A suitable strategy for creating soft yet robust and stretchable interconnections in the aforementioned technological applications is to use print-related techniques to pattern conductors on top of elastomer substrates. In this study, some thin elastomeric sheets—two forms of medical grade thermoplastic polyurethanes and a medical grade silicone—are considered as suitable substrates. Their mechanical, surface, and moisture barrier properties—relevant for their application in soft and wearable electronics—are first investigated. Various approaches are tested to pattern conductors, based on screen printing of 1) conducting polymer [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)] or 2) stretchable Ag ink and 3) laser scribing of laser-induced graphene (LIG). The electromechanical properties of these materials are investigated by means of tensile testing and concurrent electrical measurements up to a maximum strain of 100%. Performance of the different stretchable conductors is compared and rationalized, evidencing the differences in onset and propagation of failure. LIG conductors embedded into MPU have shown the best compromise in terms of electromechanical performance for the envisioned application. LIG/MPU showed full recovery of initial resistance after multiple stretching up to 30% strain and recovery of functionality even after 100% stretch. These have been then used in a proof-of-concept application as connectors for a wearable tattoo biosensor, providing a stable and lightweight connection for external wiring.

Tags conducting polymers, elastomers, Francesco Greco, Laser-Induced Graphene, screen printing, stretchable conductors, wearable electronics

Conferences & Posters News Publications

Paper on Multiresponse Soft Acutators published in ACS Applied Polymers

Post author By Alexander Dallinger
Post date March 10, 2021

“Multiresponsive Soft Actuators based on Thermoresponsive Hydrogel and embedded Laser-Induced Graphene”

Alexander Dallinger, Paul Kindlhofer, Francesco Greco and Anna Maria Coclite
Publication Date: March 9, 2021
https://doi.org/10.1021/acsapm.0c01385

Short presentation of the multiresponsive actuators

Abstract

The method of converting insulating polymers into conducting 3D porous graphene structures, so called laser-induced graphene (LIG) with a commercially available CO₂ laser engraving system in an ambient atmosphere, resulted in several applications in sensing, actuation and energy. In this paper we demonstrate a combination of LIG and a smart hydrogel (poly(N-vinylcaprolactam) – pNVCL) for multiresponsive actuation in a humid environment. Initiated chemical vapor deposition (iCVD) was used to deposit a thin layer of smart hydrogel onto a matrix of PDMS and embedded LIG tracks. An intriguing property of smart hydrogels, such as pNVCL, is that the change of an external stimulus (temperature, pH, magnetic/electric fields) induces a reversible phase transition from a swollen to a collapsed state. While the active smart hydrogel layer had a thickness of only 300 nm (compared to the 500 times thicker actuator matrix), it was possible to induce a reversible bending of over 30° in the humid environment triggered by joule heating. The properties of each material were investigated by means of scanning electron microscope (SEM), Raman spectroscopy, tensile testing and ellipsometry. The actuation performances of single-responsive versions were investigated by creating a thermoresponsive PDMS/LIG actuator and a humidityresponsive PDMS/pNVCL actuator. These results were used to tune the properties of the multiresponsive PDMS/LIG/pNVCL actuator. Furthermore, the capabilities of self-sensing were investigated. By getting a feedback from the piezoresistive change of the PMDS/LIG composite the bending angle could be tracked by measuring the change in resistance. To highlight the possibilities of the processing techniques and the combination of materials, a demonstrator in the shape of an octopus with four independently controllable arms was produced.